Cathode ray tube employing index phosphor elements adhered to a color selective electrode

Abstract

A color cathode ray tube includes an automatic convergence unit employing index elements on the reverse surface of a color-selective electrode. The paste used for forming the index elements has a composition consisting essentially of index phosphors, an inorganic adhesive and water to assure the adhesive force of the index elements onto the color selective electrode to prevent peeling of the index elements while facilitating the coating operation for formation of the index elements.

What is claimed is: 
     
       1. A color cathode ray tube comprising a tube bulb having means for producing cathode rays,   deflecting means outside of said tube bulb for controlling the direction of the cathode rays emitted by said cathode ray producing means,   a color-selective electrode in said tube bulb and adapted for color-selecting said cathode rays and projecting the color-selected rays on the phosphor surface formed on the inner surface of said tube bulb,   index element means formed on the surface of said color-selective electrode facing to said cathode ray producing means,   means for sensing signals produced when said cathode rays are projected onto said index element means, and   an automatic convergence unit responsive to output signals of said sensing means to control said deflecting means,   wherein the improvement comprises said index element means comprising a paste consisting essentially of a mixture of index phosphors, an inorganic adhesive and water and is formed by being coated and dried in situ on said surface, said paste having a composition represented by the formulae   M/P≧0.25,       0.6≦P/(m+w)≦1.2, and       m/(m+w)≦0.6     wherein P denotes the weight of the index phosphors in grams, M the weight of said inorganic adhesive in grams, m the volume of said inorganic adhesive in milliliters and w the volume of the water in milliliters.